content: /*
   * Copyright 2011-2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package ix;
  
  import java.util.*;
  
  /**
   * A base iterator that manages
   * the state between hasNext() and the next() calls; plus defines
   * the remove() to throw UnsupportedOperationException.
   * @param <R> the result value type
   */
  public abstract class IxBaseIterator<R> implements Iterator<R> {
  
      /** Indicates a value is available for consumption. */
      protected boolean hasValue;
  
      /** Indicates there are no more data available. */
      protected boolean done;
  
      /** The current value if hasValue is true. */
      protected R value;
  
      /**
       * Move the stream forward by a single element.
       * @return what the hasNext should return
       */
      protected abstract boolean moveNext();
  
      @Override
      public final boolean hasNext() {
          boolean b = hasValue;
          if (!b) {
              if (!done) {
                  return moveNext();
              }
          }
          return b;
      }
  
      @Override
      public final R next() {
          if (!hasValue && !hasNext()) {
              throw new NoSuchElementException();
          }
          R v = value;
          hasValue = false;
          value = null;
          return v;
      }
  
      @Override
      public void remove() {
          throw new UnsupportedOperationException();
      }
  }
  